const config = function(target) {
  target.prototype.$set = () => {
    console.log(0)
  }
}

@config
class Body {
  state = {
    name: 'zhangsan'
  }

  constructor() {
    this.age = 100
  }

  sayAge() {
    console.log(this.age)
  }
}

export default new Body()